EVERYONE stand as close as possible on TOP of the boss. Not near him, ON HIM. The further away you are, the more damage you will take. When paired with Yellow/Black, be ready for healing armageddon. Healers and DPS with cooldowns, vocalize them and chain them to get through this. I would pop tranq, and once it was down, pally popped his. If we needed more, warrior popped rallying cry or feral popped tranq.

Adds will be beating on people, including healers or the DPS. If you have a DPSer continuously dieing, they may want to consider using a resist trinket such as Mirror of Broken Images (TB Trinket).

BLUE:When you get your first blue, use mana cooldowns and slowly whittle the blue down to about 15%. Then, when the next oozes spawn, determine if:

a) your healers are low on mana

b) you have a blue in the next ooze spawn

If there is a blue in the next ooze spawn, WAIT on popping the current, low-health void until AFTER the new mana void has been created and is DONE draining mana--this will take a few seconds. Then, slowly whittle down the new mana void in time to renew your decision for the next set of oozes.

However, if you have a red coming and your healers don't need the mana yet, ignore the void. Trying to position yourself to be in range of a drifting void with red forcing everyone to stand on the boss will spell a wipe. If red is coming and you DO need mana, pop it ASAP and either hope you can get it down during the ooze-killing phase, or that your healers are in range to get the mana.

PURPLE:

If you've been prioritizing killing purple on normal, then this is going to be a "new mechanic" for your raid. Make sure all of your healers understand what this ooze does: it is ENTIRELY on them!

Use healing assignments and add the debuff "Deep Corruption" to your raid frames, making certain you can track the stacks. Do NOT stack up to 5 on any given person: stop at 4 stacks. Every heal you cast on a person (that you TARGET and CAST upon that person) will give them a stack. Additional HoT ticks, efflorescence, and similar will not add a stack count.

Refreshing lifebloom counts as one stack, whether refreshed by LB or regrowth. Keep lifebloom rolling on the tank if you can; if not assigned to the tank's party, then I've heard a suggestion to roll it on a pet instead for replenishment purposes

Personally, I avoided WG on this because I was worried it would add a stack to everyone, so I don't know how it is handled for certain, but I was quite able to heal my party without it.

A single rejuv on a dps is very powerful; a swiftmend on them after, especially when they are stacked on the tank, provides additional healing to everyone.

Swiftmend counts as its own stack; efflorescence does NOT cause a stack.

I think of Purple like it turns every raider into a water balloon. A water balloon filled with acid. Every heal I cast on them adds water to the balloon. Five fills, and it explodes in a shower of painful face-melting doom across the whole raid.

Huh. We actually hadn't considered that... the last one was a suggestion we just copied over from another guild :) May change that up in the future. DPS time on adds is DPS time not on the boss and my mana void!